CHANGES IN BLOOD-PRESSURE AND CARDIAC-OUTPUT DURING MAXIMAL ISOKINETIC EXERCISE

This study was undertaken to determine the blood pressure (BP) and cardiac output (Q(c)) responses to maximal isokinetic exercise. The subjects (n = 5) performed unilateral knee extension/flexion exercise (knee exercise) and unilateral elbow extension/flexion exercise (elbow exercise) at 0.52, 1.57, and 2.62 rads.sec-1. The BP was monitored using a cannula placed in the radial artery. Heart rate (HR), stroke volume (SV), and Q(c) were measured by impedance cardiography. In response to isokinetic exercise, HR and Q(c) increased significantly (p < .01), while the SV did not. The BP response was characterized by significant increases in systolic, diastolic, and mean arterial pressure (MAP) (p < .01). The Q(c) and MAP, responses were not influenced by the exercise velocity. The adjustments in HR, MAP, and rate pressure product (RPP) to the elbow exercise were qualitatively similar to those seen during the knee exercise, but the absolute values achieved were smaller (p < .05). Compared with maximal dynamic exercise, the HR and SV responses to the knee exercises were lower. The MAP response to isokinetic exercise equaled the highest value achieved during dynamic exercise. Findings from the present study suggest that the cardiovascular stress (the increase in HR, MAP, and RPP) associated with isokinetic exercise is independent of the velocity of movement and is proportional to the active muscle mass.